The world’s most powerful ocean current could weaken as melting Antarctic ice sheets release large amounts of freshwater, researchers warned on Monday, highlighting potentially severe climate impacts. Using one of Australia’s most advanced supercomputers, scientists modeled how these ice sheet changes could disrupt the Antarctic Circumpolar Current, a key driver of global climate systems.
The scientists found that the ice sheets dump vast amounts of fresh water into the ocean, changing its density and making it harder for cold water to circulate between the surface and the depths. This will have flow-on effects that could alter the ocean’s climate for centuries and accelerate sea level rise.
Melting ice sheets also dump warm water into the deeper parts of the ocean, changing its temperature and salt content. This may also make it easier for warmer, saltier waters to reach Antarctica, speeding up the melt of the continent’s ice sheets and pushing up sea levels.
Oceans play vital roles as climate regulators and carbon sinks. The strength of the Antarctic Circumpolar Current – a clockwise current four times bigger than the Gulf Stream that links the Atlantic, Pacific, and Indian Oceans – helps control ocean temperatures around the planet by absorbing heat from the atmosphere and preventing warmer water from reaching the continent.
However, if the oceans become less well-regulated, the impact on humanity and marine life could be severe. A slowed Antarctic Circumpolar Current would affect the world’s climate systems in ways we can’t fully understand or predict. Rising seas, weather changes, and ocean life starvation are just a few of the possible outcomes.
A slowdown of the Antarctic Circumpolar Current could cause the ocean to heat faster in areas close to the melting ice sheets, causing them to melt more quickly and potentially triggering a positive feedback loop. If that happens, it could speed up global warming and lead to the runaway collapse of the Earth’s ice sheets.
While global climate models are increasingly predicting a faster melt of the Antarctic ice sheet, scientists are still struggling to fully measure the extent of the melting and how it will affect the underlying oceans. They are racing to identify melting patterns and assess their findings’ potential impacts.
Scientists can track how much ice is melting from space with the help of new satellite sensors. They can also study the ice from the ground, including at the continent’s edges, where it flows out into floating plates of ice known as ice shelves. The ice shelves help stabilize the ice sheets by holding them up from below, but the melting of their undersides pushes the ‘anchor point’ back and accelerates the ice flow off Antarctica. They are also studying how melting ice shelves might influence global ocean circulation. Using satellite measurements, they are developing new models of how ice and the ocean interact.